On 28 Jan, Ivan Dimkovic wrote:
> Well.. there are several alternative methods, check out the method
> implemented in PEAQ (ITU-R 1387) and Frank Baumgarte's 'non linear' model.
> Instead of computing tonality, these models perform exponential additions of
> individual maskers, so the final effect is very similar to tonality
> estimation (why? - because tones are built on individual "peaks" and noise
> contains many similar spectral lines)
>
> It is very important that one that implements this approach tunes-up the
> "alpha" factor of smearing, so the pure noise and pure tone gives masking
> powers according to Zwicker's data. I figured out that "alpha" factor
> depends on window size and partition band median bark value.
>
> I have tried this approach in the AAC encoder, but the problem of this model
> is its speed - it requires lots of 'pow()' calculations in
> spreading-function convolution process, and therefore it is not really
> useful in real-time conditions. However, according to Baumgarte - it gives
> much better masking estimation. However, FhG encoders do not use this.
If someone wants to experiment a little bit with it: I've commited a
part of Frank Baumgarte's non linear model to LAME's psymodel.c
recently. To use it you have to set the environment variable CONFIG_DEFS
to '-DNON_LINEAR_PSYMODEL' and run configure.
Bye,
Alexander.
--
To boldly go where I surely don't belong.
http://www.Leidinger.net Alexander @ Leidinger.net
GPG fingerprint = C518 BC70 E67F 143F BE91 3365 79E2 9C60 B006 3FE7
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